Conventional internal radioactive contamination whole-body counters are configured so that two upper and lower radiation detectors are installed in front of a measurement space in the whole-body counter in order to measure internal radioactive contamination of a radiation worker. Thus, the upper and lower radiation detectors of the whole-body counter measure radiations emitted from the body of the worker contaminated with internal radiations, add the measured radiations, and calculate a value of measurement of the internal radiations. Particularly, when a radioactive material inhaled by the radiation worker is located in an upper portion of the body, the upper radiation detector of the whole-body counter measures relatively more radiations. However, when the inhaled radioactive material is located in a lower portion of the body, the lower radiation detector measures relatively more radiations.
Meanwhile, another type of whole-body counter used to determine the internal radioactive contamination of the radiation worker and to measure the contaminated radiations is equipped with one radiation detector installed in front of the measurement space. This whole-body counter measures the radiations emitted from the body of the measurement target while the radiation detector slowly moves from the top to the bottom, and calculates internal radiations using a value of measurement of the radiations. Since there is no radiation shielding wall in front of the measurement space, natural radiations or surrounding scattered radiations may be introduced into the radiation detector when the whole body is measured. Thus, the value of measurement of the radiations may have an error value. For this reason, the whole-body counter having the upper and lower radiation detectors in which the natural radiations are shielded is mainly used.
Typically, to monitor the internal radioactive contamination of the worker in radiation use facilities and atomic energy related facilities, radiation measurement is performed on all workers who have a possibility of inhaling radioactive materials during radiation work using an internal radioactive contamination whole-body counter. Meanwhile, the radioactive materials introduced into a human body are characterized in that they are uniformly distributed in a whole body or are concentrated and deposited in a specific organ such as a thyroid gland, a lung, or a hypogastrium. Thus, to increase precision of a radiation measurement value according to a deposition location of the radioactive materials when the internal radiations are measured and to correct the measurement value, the internal radioactive contamination whole-body counter is designed to be able to apply four measurement geometries for the whole body, the thyroid gland, the lung, and the hypogastrium to perform the measurement. However, since it is typically impossible to know accurately in which location of the human body the radioactive materials inhaled by the worker are deposited, the internal radiation measurement is performed using the whole-body measurement mode for calculating a highest or conservative radiation measurement value. The whole-body measurement mode of the internal radioactive contamination whole-body counter is adapted to calculate the highest measurement value on the assumption that the radioactive materials introduced into the human body are uniformly distributed in the whole body, and to calculate a value that is 2.5 to 1.5 times higher than a value obtained by measuring the internal radiations using the other measurement mode such as the thyroid gland, lung, or hypogastrium measurement mode even when the worker inhales the radioactive materials of the same concentration. This whole-body measurement mode has a problem in that a dose of radiation exposure of the radiation worker is incorrectly estimated in a very conservative way, because it not only fails to properly indicate the internal radioactive contamination location of the radiation worker but also calculates the internal radiation measurement value as a high value. Meanwhile, the dose of radiation exposure of the radiation worker is regulated so as not to exceed an annual dose limit. Thus, by conservatively calculating the internal radiation measurement value as a high value, wrong information about the dose of radiation exposure is provided to the radiation worker, which may increase a risk of industrial accidents such as occupational diseases due to the outbreak of radiation excessive cancer resulting from excessive exposure in the future.
A whole-body counter for discrimination between internal and external radioactive contamination is disclosed in Korean Unexamined Patent Publication No. 10-2011-0033614, in which the precision of radioactive contamination measurement is improved by additionally installing a plurality of radiation counters on conventional internal radioactive contamination measuring equipment to discriminate between internal and external radioactive contamination of a worker. However, Korean Unexamined Patent Publication No. 10-2011-0033614 does not provide a function of determining in which location of a human body radioactive materials inhaled by the radiation worker are deposited, and thus has a disadvantage in that a radiation measurement value is not accurate because internal radiations are measured using only a whole-body measurement mode regardless of the location contaminated with the radioactive materials, and thus a dose of radiation exposure of the worker is conservatively (excessively) estimated.
Technical Problem
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a whole-body counter providing an optimized measurement mode capable of determining a radioactive contamination location in a human body using a measurement ratio of upper and lower radiation detectors and of increasing precision of radiation measurement, and a radiation measuring method using the same.
Technical Solution
According to an aspect of the present invention, a radiation measuring system based on an optimal measurement mode includes: a whole-body counter having upper and lower radiation detectors that are installed in front of a measurement space, which has an inlet passage and is formed in a housing, and that detect respective internal radiations of a measurement target and then first and second internal radiations of a body region corresponding to one of a thyroid gland, a lung, a whole body, and a hypogastrium; and a processor controlling to determine an internal radioactive contamination location of the measurement target based on a ratio of the first and second internal radiations, to apply the optimal measurement mode corresponding to the ratio of the first and second internal radiations, and to additionally detect the first and second internal radiations of a body region corresponding to the determined internal radioactive contamination location.
According to an aspect of the present invention, a radiation measuring method based on an optimal measurement mode includes: detecting first and second internal radiations of a measurement target using respective upper and lower radiation detectors installed in front of a measurement space that has an inlet passage and is formed in a housing; calculating a ratio of the first internal radiation of the measurement target which is detected by the upper radiation detector and the second internal radiation of the measurement target which is detected by the lower radiation detector; determining whether the ratio of the first and second internal radiations belongs to a first range, a second range, a third range, or a fourth range; applying one of a thyroid gland measurement mode, a lung measurement mode, a whole-body measurement mode, and a hypogastrium measurement mode according to a result of the determination to detect the first and second internal radiations of a body region corresponding to one of a thyroid gland, a lung, a whole body, and a hypogastrium; and adding and outputting the detected first and second internal radiations of the corresponding body region.
Advantageous Effects
As described above, the internal radioactive contamination whole-body counter of the present invention determines an internal radioactive contamination location on the basis of a measurement ratio calculated by the upper and lower radiation detectors in connection with the internal radioactive contamination of a worker which may take place during radiation work, and applies an optimal measurement mode based on the contamination location to provide an internal radiation measurement value.
The conventional internal radioactive contamination whole-body counter does not provide a function of determining in which location of a human body radioactive materials inhaled by a radiation worker are deposited, and thus has a disadvantage in that internal radiation is measured using only a whole-body measurement mode regardless of the location contaminated with the radioactive materials, and in that a dose of radiation exposure of the worker is conservatively estimated. However, the whole-body counter of the present invention determines the internal radioactive contamination location of the radiation worker and thus provides an optimal measurement mode based on the contamination location, thereby improving precision of the internal radiation measurement.
Korea Hydro & Nuclear Power Co. Ltd. allocated expenses of about 35 billion wons from 1991 to 2000 in observing the radiological protection recommendations of the International Commission on Radiological Protection and reducing the radiation exposure of radiation workers of nuclear power plants, and expenses of about 190 billion wons from 2001 to 2010 in reducing the radiation exposure. In this way, reduction of the radiation exposure of radiation workers is closely related to the operation of the nuclear power plant. The radiation measurement performed conservatively at present is more accurately performed, and thereby it is expected that potential operation expenses of the nuclear power plant can be greatly reduced.